Gulf of Maine Warming Update: 2022 the Regions Second Warmest Year
Documenting one more year in a decade of above-average regional temperatures
Annual Sea Surface Temperatures
With an annual average sea surface temperature (SST) of 53.66°F — more than 3.72°F above normal — the Gulf of Maine experienced its 2nd warmest year on record in 2022. This year fell short of the previous warmest year on record — 2021 — 0.43°F, but was record-breaking in a number of regards.
In nine of the twelve months this year, average monthly SST was within the top 3 warmest among all years. The most extreme temperatures this year occurred in November and December, each setting new record highs. Monthly temperatures ranked lowest during July and September (ranked 8th and 6th respectively), but were still within the top ten for each of those months. These temperatures all contribute to what has been a decade-long pattern of above-average temperatures in the area.
Annual Trends in Sea Surfacae Temperature
Since the early 1980s, the rate of warming in the Gulf of Maine 0.86°F / Decade has been more than triple that of the world’s oceans (0.27°F / Decade Figure 1). The rapid warming in the Gulf of Maine began to catch scientists’ attention around 2012 when temperatures jumped to new record highs. Since then, annual average SST has remained high, contributing to the Gulf of Maine’s distinction as one of the fastest warming locations globally.
The observed rate of warming in the Gulf of Maine varies throughout the year. Comparisons across four, three-month periods (Figure 2) reveal that the Gulf of Maine is warming fastest during July-September (nearly 4x the global ocean average), more than twice the rate seen during January-March (~3x the global ocean average).
In addition to within-year variation, there can also be significant spatial variability in annually-averaged SST patterns. The Gulf of Maine in 2022 illustrated this fact with the region southeast of Georges Bank experiencing the highest SST anomalies (Figure 3). This area is more susceptible than other areas of the Gulf of Maine to large-scale variability in major oceanic currents, such as the relative influence of the Gulf Stream versus the Labrador Current.
Looking at these spatial patterns in three-month averages (Figure 4) shows just how “patchy” these pockets of above-average temperatures can be. During January-March, the areas to the south and southeast of the Gulf of Maine exhibited a strong mix of both above and below average surface temperature. In April-June the size and number of below-average SST patches declined. By July-September the water within the Gulf of Maine itself and the deeper waters just south of Georges Bank experienced warmer temperatures than the surrounding areas. And in October-December, the influence of the Gulf Stream warmth is evident along the shelf break (200m contour), while the Gulf of Maine itself remained several degrees above the long-term average.
When we compare the annual average SST for 2022 (53.66°F) to other years in the Gulf of Maine, we see that it was ~0.4°F cooler than 2021, the warmest year on record(54.09°F). When we look at the deviation from the long-term average SST (i.e., the annual SST anomaly), the last decade stands out for its exceptional warmth (Figure 5). 2022 extends a pattern that began in 2010 of sustained above-average temperatures. With the exception of 2019 (ranked 13th), all of the last ten years remain in the top 10 for SST.
Worldwide Temperatures
It was not just the Gulf of Maine that experienced exceptional warmth in 2022, however. Globally, 2022 was the 3rd warmest year for sea surface temperatures, and 6th-warmest year for combined land & ocean temperatures..
Figure 6 shows annual average SST anomalies for oceans all over the world in 2022. While much of the Southern Ocean and expanses of the southeastern Pacific were anomalously cool (a feature of La Niña conditions), most of the world’s oceans experienced unusually warm temperatures in 2022. This is particularly true for northern mid-latitudes, especially the northwestern Pacific (off Japan) and along the eastern seaboard of the United States—a region that includes the Gulf of Maine.
Daily Sea Surface Temperatures
The annual cycle of SST in the Gulf of Maine exhibits a familiar pattern with the lowest temperatures observed in March, with the highest SSTs observed in August (Figure 7). The average difference between the annual maximum SST in August and the annual minimum SST in March is 22.87 °F. In 2022, the difference between the maximum SST (Aug-07, 68.72°F) and minimum SST (Mar-19, 42.15°F) was 26.57 °F. Daily SST anomaly values in 2022 never fell below +1.59 °F and reached as high as +7.36 °F above the long-term average. The largest temperature anomalies were observed on November 7th, when they breached 7 °F above the long-term average.
Record Setting Daily Temperatures
Daily SST values in 2022 were some of the highest ever recorded in the Gulf of Maine. Record daily high SSTs were set for more than half of all days in November and December, with new records set in all months but July (?@fig-percent-record-bars). The most daily records for a single month occurred in November, which experienced record high SSTs for 24 of the month’s 30 days - or 80% of the month. In total, record high daily temperatures were reached on 169 days in 2022; nearly 46% of the year experiencing record high SSTs.
More Persistent, Intense Heatwaves
A marine heatwave (MHW) is defined as a period when there are five or more consecutive days when the observed SST is greater than the 90th percentile of the long-term average for that day. Gaps of 2 days or less in this threshold do not constitute a break in the MHW event.
Figure 7 shows the long-term average SST (line labeled “Climatological Mean”), as well as the threshold for being a MHW day (line labeled “Heatwave Threshold”) or a marine cold spell MCS day (line labeled “Cold Spell Threshold”). The colored line and shaded area in the figure shows the observed SST for that day and its distance from the climatological average; when it is red, the Gulf of Maine is experiencing MHW conditions. The Gulf of Maine met the criteria for MHW status for 353 days in 2022.
Comparing daily SST anomalies and MHW status for 2022 to the long-term record (Figure 9), as in the figure below — it becomes clear that the frequency, duration, and intensity of MHWs has not only increased in the past decade. In a world without human-caused climate change, we would expect, positive (warm) and negative (cool) SST anomalies to more or less balance out over the span of several years, as various patterns of natural climate variability alternate having a dominant influence in Earth’s climate (e.g., La Niña vs El Niño). What is being observed in the Gulf of Maine (and elsewhere around the world), however, is a loss of that balance: larger fractions of recent years are experiencing above average temperatures and cold spells are becoming vanishingly rare.
Warming Rate
GMRI research was the first to reveal that the Gulf of Maine has been warming faster than the vast majority of the world’s ocean. Figure 10 updates this historical analysis by including data for 2022. Indeed, the story has not changed: the Gulf of Maine is warming faster than ~96.6% of the world’s ocean. The reason why this is so important is because the rate of change can have profound consequences for the biology of individual species and for the integrated ecology of entire food webs. Marine species are responding to warming trends by adjusting their latitudinal range and the depths that they occupy in attempts to track their preferred conditions. Not all species are capable of tracking rapid environmental change, and scientists are concerned that ecosystem resilience will decline as the environment outpaces the communities they once supported.
Concluding Thoughts:
In recent years, SSTs in the Gulf of Maine (and adjacent waters) have increased significantly and the rate of warming has accelerated. Combined, these climate-related impacts are beginning to have profound consequences for the marine ecology in the Gulf of Maine, with implications for the people and communities who rely on marine resources for their livelihoods and well-being. Research suggests there are two major factors driving these trends, one oceanographic and one atmospheric:
Oceanographic: The Gulf of Maine is influenced by two primary oceanic currents: the Labrador Current and the Gulf Stream. Historically, there was a stronger influence of the Labrador Current on the water in the Gulf of Maine. That stronger flow helped keep the heat transported northward along the U.S. East Coast by the Gulf Stream further out to sea. More recently, scientists have observed changes occurring in the interplay between the Labrador Current and Gulf Stream. More Arctic-origin freshwater from melting sea ice and land-based ice is constricting the southward flow of the Labrador Current. This is allowing the Gulf Stream—which transports warm water from lower latitudes to spread out more at latitudes around the Gulf of Maine. This, in turn, allows warmer water, more heavily influenced by the Gulf Stream to “spill over” into the Gulf of Maine.
Atmospheric: The North Atlantic Oscillation (NAO)— a large-scale pattern of natural variability in the atmosphere — has been in a “positive phase” more frequently over the past 10-15 years, meaning a more zonal (i.e., west-to-east) atmospheric pattern has dominated in the region. The relative decrease in “waviness” of the jet stream inhibits more consistent intrusions of cooler, Arctic air into the region.
While the oceanographic driver of the observed SST change in the Gulf of Maine has clear links to human-caused climate change, more research is needed to ascertain whether the NAO is experiencing significant changes as a result of anthropogenic climate change. Regardless, the atmospheric and oceanic conditions of the past several years combine to reveal an unambiguous trend: The Gulf of Maine is experiencing unprecedented warmth—and is heating up at a rate that is faster than almost anywhere else in the world’s oceans.
A Note on Data Sources
- NOAA High Resolution SST data provided by the NOAA/OAR/ESRL PSL, Boulder, Colorado, USA, from their Web site at https://psl.noaa.gov/data/gridded/data.noaa.oisst.v2.highres.html.
Recommended Citation:
Gulf of Maine Research Institute. 2022. Gulf of Maine Warming Update: 2022. https://gmri.org/stories/warming-22
Marine Heatwave Technical Report Preview:
The study of Marine heatwaves is a relatively new area of study. Scientists here at GMRI were first to use the phrase when they brought public attention to the extreme temperatures in the Gulf of Maine during 2012. The concept of a “marine heatwave” emerged as a way to communicate a rare phenomenon where temperatures were much higher than the observed historical and seasonal fluctuations. These extreme conditions caught scientists’ attention for their ecological & economic consequences, and they became a tool for studying future climate-change-related impacts before they occur elsewhere.
As temperatures increase globally, SST observations that were once rare have become more and more common. Understanding this pattern, scientists now are considering new ways to define what it means to be a marine heatwave. Debate has now emerged on how “best” to identify and measure the impacts of these rare events. GMRI scientists are part of this evolving discussion among the international community that is weighing the trade offs in these proposed changes.
In an upcoming technical report series, GMRI scientists will be covering this discussion in detail. Explaining the rationale between the competing approaches, how scientists think about their impacts, and how the heatwave record for the Gulf of Maine can change with these decisions.
OLD ASSETS:
Temperature Anomaly Horizons
One way to think about the severity of these changes is to think about temperature horizons. A temperature horizon captures how long temperatures remain above certain thresholds. Each threshold is designated its own temperature, and in this way we can see how long within a year temperatures remained: 1 to 2 or as much as 4\(^oC\) above normal.
Comparing the Gulf’s Two Hottest Years
If we pull the horizons of our two hottest years on record it makes it easier to contrast where either one experienced acute high temperature events, and where there were sustained periods of above average temperatures.
Early into 2022 it was apparent that the year was on-par with the previous title-holder for warmest year on record.
The Balance of Hot and Cold
Another way to visualize the climate transition that we are observing is by looking at the fraction of each year spent in different temperature ranges. Under a steady climate we would expect over the long-term to spend similar amounts of the year experiencing relatively warm & cold temperatures. These periods would balance themselves out and we would on-average have experienced something similar to the long-term climate.
What we have been seeing in the Gulf of Maine recently has lost that sense of balance. Larger fractions of the year are shared by above average temperatures & cold spell events are becoming vanishingly rare.
